The present invention generally relates to a device for synchronizing at least two converters and more specifically a device for synchronizing at least two variable frequency voltage step-down/step-up (DC/DC) current converters for a vehicle.
Existing interlaced multi-phase converters in the automotive industry function at fixed frequency (e.g. 150 kHz for each phase). However, conducted and radiated emissions are present on a narrow radio frequency spectrum and filters are necessary to meet the required EMI standards for vehicle components.
In addition, converters operating at a fixed frequency do not maintain regulation stability at duty cycles in excess of 50% and this limits the power output of the converters.
In addition, these fixed frequency interlaced converters, in principle, require a minimum control duty cycle (e.g. 1%) to maintain a phase-lock loop stability of the output voltage. This principle thus involves consuming at least a current load of a few amperes, which suggests poor performances.
Variable frequency converters are hard to interlace. Synchronized operations of several converters operating at different frequencies is difficult to implement because it requires complex systems namely when synchronizing is required over an extended range of frequencies.
Synchronism often requires a digital device to calculate at each period the exact synchronization moment for each converter. In general the operating frequency range is very limited.
Moreover, the synchronizing device usually generates a total shutdown of all converters when the device fails.
U.S. Pat. No. 7,933,132 describes a system including multiple variable frequency converters, a synchronization circuit associated to each converter to synchronize same frequency operation of each converter and a control device for synchronizing the operation of synchronization circuits.